Facsimile telegraph system



5 Sheets-Sheet l W. B. BLANTON ETAL FACSIMILE TELEGRAPH SYSTEM FiledvOCt. ll, 1939 Dec. 9, 194i W. B. ELAN-ION ET AI. v2,255,339 FACSIMILE TELEGRAPH SYSTEM D@ 9, wm.

Filed Oct. 1l, 1939 5 Sheets-Sheet 2 TRANSMITTING AMPLIFIER l EIB 'INVENTORS w. B. BLANToN F. I .CURRIE G.w.-.IANsoN I .G.sTEwART R. J. wIsE TTORI FIG. 3

Dec 9, 194i w, B. BLANTON ET AL FACSIMILE TELEGRAPH SYSTEM Filed Oct. 1l, 1959 5 Sheets-Sheet 4 Y Dec. 9, 1941. w, B BLANTQN ETAL 2659339 FACSIMILE TELEGRAPH SYSTEM F'ileadv Oct. ll, 1939 5 Sheets-Sheet 5 FIG. 6

AMPUFIER 8 |99 362 3 2 |76 INVENTORS w. B. BLANToN l.. CURRIE .w. JANsoN Patented Dec. 9, 1941 William B. Blanton,

Merrick, -N. Y., and Frank Leslie Currie, Plainield,

George W. Janson,

Nutley, VLouis G. Stewart, Rutherford, and

Raleigh The Western J. Wise, Dunellen,'N.

Union Telegraph Company,` New J., assgnors to York, N. Y., a corporation of New York l Application October 11, 1939Serial No. 298,872 Y l 21 claims. (ci. its- 6.6)r

This invention relates to communication systems and has particular reference to a novel telegraph system employing facsimile equipment and comprising a plurality of stations such as subscribers substations or telegraph branch oices having circuits which are concentrated at a central point such as a telegraph main office.

The primary object of the invention is to provide automatic switching facilities whereby any one of a plurality of substations may be connected with a central station for communicating purposes.

Another object of the invention resides in the provision of a system employing switching means for automatically connecting located in a main oice to any one oi a plurality of branch oiiices and in which said switching means is normally controlled exclusively from the branch oice after the connection is made.

Still another object of the invention is to provide an organization of instrumentalities whereany one of a plurality of branch offices may be connected to a main oflice for transmitting or receiving over a single circuit and in which the automatic switching apparatus employed to ,connect a branch oice transmitter with a central olce rec-order is rendered responsive to a call initiated at said branch oice and unresponsive to a call initiated at the central office and destined for one of said plurality of branch oices.

A further object of the invention is to provide, in a system in which a plurality of substations are associable with a main station by means of concentrator switching apparatus, means whereby a connection established between one of the substations and the main station is maintained until released'from the substation.

A still further object of this invention is 'to provide, in a concentrator employing multi-contact stepping switches, means for securingv a low resistance of the contacts of said switches.

Another object of the invention is to provide facilities whereby one -or more of a plurality of substations associable by automatic switching apparatus with any of a limited number of main station recorders are given a preferred status permitting seizure of the first one of said recorders to become idle.

Still another object of the invention is to insure complete transmission of messages by novel guard features.

Further objects will become apparent from the following description of an illustrative embodiment of the invention taken in conjunction with the accompanying drawings of which:

facsimile apparatusv Fig. 1 is a schematic representation of a facsimile concentrator system embodying the invention; Y Y

Fig. 2 shows the arrangement oi" Figs. 3, 4, 5

- and 6 assembledas aV system in accordance with the invention;

Fig. 3 is a diagrammatic showing of one form of substation or branch oice facsimile apparatus; Fig. 4 illustrates the circuits comprising one unit of the concentrator switching apparatus;

Fig. 5 is a diagrammatic representation of one central station recording apparatus; and

Fig. 6 shows diagrammatically one facsimile transmitting apparatus of the central station.

Having referencerstlto Fig. 1, there is shown a plurality of facsimile substations Aor branch oices A, B, C, D and E, eachv of which is connected by means ofindividual'communication channels I I with a central station M. Switching'` .equipment I2 is located at the central station and is used to connect any `of the channels II to any one of a plurality of recording instruments I3, I4 and I6. A plurality of jacks Il, one for each channel, are alsol located in the central station M. A plurality Otcentral station facsimile transmitters I8 are each provided with a plug I9 Y for the purpose of connecting the transmitters with any of the communication channels I I by insertion in one of the jacks Il.

Associated with each recorder in a .steppingy switch such as 2I, 22 .and 23 for the purpose of connecting a recorder to any oi the channelspII which are terminated in multiple on the contacts of the stepping switches. Individual relay apparatus 24, 26, 2l, 28 and 29 is associated with each of thecommunication channels and eachis responsive to a start or calling signal initiated atY its associated-substation yfor the purpose of actuating one of the stepping switches to connect a recorder with thecalling substation. An answernextY switch is associated with each facsimile recorder for thepurpose of routing an. incoming call to the lowest numbered idle recorder. Such switches areA 3|, 32 and 33.v As shown in Fig. l, the stepping switch 2I connects substation B with recorderk I3 and stepping switch 23 connects substation C with recorder I6. Assuming that at this time a call is initiated by substation E, the lower call registering device 29 is operated to close a circuit through the switching member 33'and its left hand contact, the switching member 32 and its right hand contact, to the winding of the steppingy switch 22. This stepping switch is actuated to travel over its contacts until connection is made to Athe communication channel y emesse' Y p i y u v associated with substation Ef in which position the drum 31 so that the carriage may be prit is arrested. Following this operation the pelled when a threaded split-nut 4'! is moved into switching members 32 and 34 are moved to their engagement with the feed screw 42. As viewed respective left hand contacts as Viewed in this in this gure the carriage 43 is normally urged figure. The engagement of the switch 34 with 5 by means of a spring 48 toward a position at the its left hand'contactcompletessa circuit :between righ-tlof'ltheadrawing.

recorder |4sand the"'substationiE-l The engagea Husedlinuthe'ccarriage :43 isv amv-optical scanment cf `the switching member 32 with its left ning device 49 including a source of light 5l and hand contact isolates the operating magnet oithe` y alight responsive device such as a photoelectric stepping switch 22 from the callinggcircuit so that 10, cell 52. Cooperating with the source of light is subsequent calls arriving at the centralstationT a"lightchopperf(not shown) for the purpose of during the operative engagement of,- recorder II4s periodically interrupting the beam of light which with substation E and of recorder lafwithfsub-f isffdi-rectedgfthroughia projector 53 onto the surstation C are passed to azrhiglrervnumbered.: facci-ofcl thelasheet'; V'I'he light reections from recorder. Following the transmissi' ffa-riiesQ-15g-tlev-sheet S'Ilaredir'ected onto the photoelectric sage between any of the substatinfs anddnoff cel-i252 infI-an'yiwell known manner, one ofwhich the main station recorders the switchirrgf-m'em K is Vshown l'in the--Wise et al., application hereinbers such as 32 and 34 are restored to theirgree before'referredtony Y spective right hand contacts provided Vthat the A recording stylus 54 is mounted on a lever 55 recorder is reconditioned for receivingias de-zo Wliicl--is normally held in its upper position by scribed `more-.fullyT hereinafter.` Thus; the, remeansofy. a: retractilaspring.. 51. The. lever 56 corderis madeavailableforthereceptionof other7^ isrranged Eto'.bepivotedinfsuch.a manner. that.A calls. the ,stylus 54 may;A be., brought.. intc. registry with.

'Ifhecsubstations AVB,v 0, .Danni` Elareprovided the. slieetl36 b`y the. energiz'ation lof an electro.- vvith. 'facsimile apparatusr Which is, capable 0L 25. magnet 58..

transmitting or recording facsimile s ignalsJh'us, Y Allsendreceiveg'rswitch lffis' included in.N the if itfisrdesiredto.transmitvsubjectmatter from apparatus eI-nplomd..to.-controlthe` opcrationof.

tlvje'lcentral. station. M toariyfone of .thesub'stathe branch'4 'oceJfac'si-m-ilimachine. When it nectioh is .iliadelcyr'V meanepn one pf the, plugs; ll 9 y. 30goie, the.'v switch l9.'fis .`1 placed. in its left` hand andfthejackl Ilvcorrespoding. ..to.y thesubstation DDSIOH, aS..Sh0WI1, andi when themachine isto that `thlefsame` communication-.channels are used' itS,right. hand position.v Thelsubstationappain bot'hltransmittingt.andreceivingjmnther. ratusis c'onditinedlforfoperationby: rst. moving branch stati-ons; vMeansarel providedf so tl'atthe 35 t a' control swit'cli. 62| itsiig'ht." hand. contact,

Switching: `ap*I ,fm-gsr located; at 15e' v cenral L gta-. thereby connecting Y ai localf source of" alternating;

sent overthecircuit-lwhen. transmission is occur.- The"opratirisloccuri' ringfpom the' centrar stann' tetue branch. menvof'tne'switciijtbi itglrighvhand Contacty Branche-Ome fplmat? tauinaiiateri'perticgof;nie:specincation...'The control T'S'Witcli is maitaihedlon itsleft handccnf In Fig. 3i there, is; shown the: facsimil'e appare tanti dwing., i d1 e. perm dsl soth'atjagsignal'.such.,asVY

ratus -a-ndithe-l.controlequipment-:thereforiwhich; a; blr 63s may b. one. .tedundr the( @Chti O1; o ff.

islocatedatsoneofthgbranch'lofces... The/1453155.60..

. .v ,A y l .v ontactsofapola drelayd. y facsunilefapparatuscomprises wcombmationlma. The. Wmdmg. dfterely? Brig icluded l a:

chinewhiehiisfcapablefoffwansmlttmglon'record simplex circuinifcrmeb'y makinga connection;

ing s' facsimile: signals: @nez types: of: suche aamaj..

to'f an intermediate; pjointofl an, impedance 665 chine is disclosed and claimedsin; aacopendingape' 1, .l t l c Y. l A. y y l y y u which 1s bridged acrosscapalr. of.l1ne..conductors. phcationfofi RMT WSeeetialrseml N-'-293"188 50' L. The 'conductersfgncensufute;.die,facsimue sig- .--1 f params-for faslmlete-egfaphyw Theffacsmla' modulatedfanerrraungrcurremf comprising theA application. isldierent in.ua;;..fewinem-essential:

l i. I A posed upon one ofA a plurality of. steady state.. respectssfrom;thatzfdisclosed. metheabove .mene 50; Cmfditionsc WE1 di .sighlgloverl theysmplx;

monediapplicationioflmw@lil#butSlnelefftheg circuits-effected.: T11-eline' connectorensweexT less capable:offproducingzthec:sameeresultaandiis.: tendedlfmm-me. substtthrman Statin taining the: subjectimatterf toubelf transmittediisf; Fgxleshows thee switching; apparatus' andthe mountedgonlaicylinder. 3J and is: secured theretog. ci-rcus'therefrof 1OriLCOfmpleteunitfoi'thefcon--4 bymeansiofsa pluralityfoncircularaelasticfmeme v65;.cent-raton equipment;. The lin'e` conductors; L bersf3-8n Ther cylinder. iszcontinuouslyfrotatedfin which areconnected with `the .branch oiiice equip-- the;directioneoflthev arrowfbyc means of a'idrivingy mentjust described: aresconnecte'dlzt'o a pair. of; motori 39: actingithroughlsuitablelreduction geare studs 6'! and .68 of a multiflevelastepping switch.

ingali'lf., Thezfdrivingbmotorsis. alsof; employed: to; 69.- The; switchingequipmentr shown,jnthepuprotatee'a feed-5 screw. 42; by;I meansofz'whichy theamiperfand'. middle portionsioffllig; 4" is @associated sheetreaisfscanned; 1 with one of the central oce recorders:` Simi- A-.lcfarriage-IB isflocatedi adiacenti-the '3F11 larequipment is1iassociatedwith each,of the other and igequippedwith sliding members-.44. f These;` central. cnice-recorders: and thesystemzislso. ole-` sldmg mange, Cooperate. withHA av pair of.railsf signedf thaty any one ofn therbranclnoices;l con,

451 eist:endingV paralleltdthe longitudinal` airisfl 755. nected to thefconcentratorequipment-1v may have;

access to any of the facsimile recorders located at the central oiiice. Accordingly, the conductors of line L which are shown connected to contacts 61 and 68 of the stepping switch 69 are also connected to corresponding contacts 1I and 12 of a stepping switch 13 which is included in the concentrator equipment associated with a second one of the central ofce recorders. Similarly, the conductors are connected to a like pair of Contact studs on each of the other stepping switches used.

An impedance in the form of an inductor 1.4 is bridged across the line conduct-ors L and is provided with a center tap which is connected by means of a conductor 16 to a line relay 11. Thus, the direct current simplex signals passing over the line conductors L are employed t control the operation of the line relay 11 which, in turn, c-ontrols local circuits at the concentrator by means of which the switching apparatus performs its function in a manner which will be described in detail subsequently.

When the stepping switch 69 has been actuated to effect contact between the terminals 61 and 68 and the respective brushes or wipers 18 and 19, and when the contacts controlled by the relay winding 8| are operated, lthe line circuit is extended to the input side of an amplifier 82. The amplified facsimile signals are then impressed upon signal inverting apparatus 83 and then applied to the recording apparatus of Fig. associated with the illustrated unit of the switching equipment.

Central oce recording apparatus v The preferred form of recording apparatus to be used with the facsimile system comprising the instant invention is shown diagrammatically in Fig. 5. The mechanical structure of such a machine is disclosed and claimed in a copending application of R. J. Wise et al., Serial No. 110,760, led November 13, 1936, entitled System and apparatus for facsimile telegraphy. The machine comprises a drum 84 which is provided with two axially extending arbors 86 and 81 and is supported for rotation between centering spindles 88 and 89 arranged to cooperate with the drum arbors. An arm 9| is pivoted on the spindle 88 and extends in the direction of the drum to engage a pin 92 projecting radially from the spindle and also a pin 93v which extends radially from the arbor 86. The arm 9| is urged into said engagement by means of a spring 94, one end of which is attached to the arm and the other end of which is attached to the spindle 83. This linkage serves to drive the cylinder 84 when the spindle 88 is rotated. Rotation of the spindle is effected by means of a driving motor 96 acting through suitable reduction gearing 91. Also included in the driving mechanism is a friction clutch 98 which permits the arresting of the shaft 88. A disc 99 having a notch formed in the periphery thereof is secured to the centering shaft 88. An arm or latch IDI is arranged to engage the peripheral notch of the disc 99 when acted upon solely by a retractile spring |02. An electromagnet |63 is provided so that, upon energization, the latch IDI is lifted and becomes disengaged from the .disc 99 and thereby permits rotation of the shaft 88.

A sheet of recording material |84 is wrapped around the cylinder 84 and secured thereto by means of a plurality of circular elastic members |06. The sheet |94 is mounted on the drum 84 so that the lap |01 formed therein invariably pears a definite relation to the notch formed in the disc 99.- Such an arrangement is for the purpose of securing the proper phasing between the recorder and the substation transmitter and will be described in greater detail subsequently.

A carriage |98 is arranged to be slidably moved on a pair of rails |89 parallel to the longitudinal surface of the cylinder 84. An electromagnet I is mounted on the carriage and, when energized, serves to pivot a lever I I2 .into the retracted position shown on the drawing. A recording stylus II3 is attached to one extremity of the lever I|2 and, as illustrated, is held out of vengagement with the sheet of recording material |84 during'idle periods. A threaded split-nut II4 is also attached to the lever I I2 and is adapted for engagement with a threaded feed screw I I6 which is rotated at a suitable speed by the driving motor 96 acting through its associated reduction gearing 91. When the electromagnet III is deenergized, the lever II2 is moved by means of a spring II1 in such a manner that the split-nut I|4 engages the feed screw II6 and the stylus II3 is brought into contact with the surface of the recording sheet |04. The engagement of the split-nut with the feed screw results in the movement of the carriage |08 toward the right, as viewed in this ligure, against the restraining action of a retractile spring IIB. Obviously, at the end of a scanning operation when the lever I I2 is pivoted to disengage the split-nut from the feed screw, the carriage is returned by means of the retractile spring I I8 to the extreme left hand position shown.

The recording machine illustrated is provided with facilities for automatically discharging a drum after a recording operation and for feeding a fresh drum into the machine. The machine is normally provided with a copious supply of such fresh copyholders or drums, one of which, II9, is shown fragmentarily. A rack or magazine is used to store the cylinders and comprises two rail members I2I and |22 mounted on a pair of supporting brackets |23 and |24 and spaced apart slightly more than the length of the cylinder 84. A pair of resilient upright members |26 and |21 are secured to the rail members |2I and |22 respectively and cooperate with an auxiliary pair of spaced rails |28 and |29 respectively to guide the stored cylinders toward the scanning device. The cylinder I I9 awaiting positioning in the facsimile recorder is held in readiness by having its arbors such as I3I supported by the upper end of a pair of detents, one of which, |32, is shown. Each of the detents is pivoted adjacent its lower end on the respective rail members and is normally held in this cylinder restraining position by means of one of a pair of resilient members such as |33 attached thereto and also to the rail member I2I.

Upon completion of a scanning operation,l a drum changing motor |34 is started and drives a worm gear |36 which in turn drives a cooperating pinion gear |31. The pinion gear is keyed to a shaft |38 upon which is also secured a pair of cams |39 and |4I. A bell crank |42 is pivoted on any convenient stationary member such as the bracket |43 and is provided with a forked portion |44 adjacent the extremity of one arm thereof land also with a rod or cam follower |46 adjacent the extremity of the other arm thereof. The rotation of the shaft |38 brings the raised portion of the cam |39 into engagement with the rod |46 thereby pivoting the bell crank |42 and bringing the bifurcated portion |44 into engagement with a pair of pins |41, attached to the centering shaft .|6l attached to one of the members -holder slightly so. that 88. Further;movement ofthe bell crank; caused .bythecontinued'rotation of the cam |39v moves the shaft; 89 toward the left as viewed in the drawing against the actionof a springv |43; one

- endofwhich is attached to a pin |49 extending from=theshaft and the other end of which is secured to a stationary bracket l I..

-. The withdrawal of the centering shaft 89 as described permits the drum 84 to drop so that the arbors86 and 81 thereof rest in a cradle formed by, grooves in a pair of members |52 and |53. Thesemembers are secured adjacent their lower extremities to a rocker shaft |54 which is suitably journaled in bearings mounted in any convenientxed brackets (not shown). Also secured to therccker shaft |54 is an arm I5Scarrying at its: outer extremity a cam followerin the form of a roller |51. Tnisroller is adapted to c0- operate with the cam |4| so that when the shaft |38 isv rotated by means of the mechanism driven bythe motor |34, the engagement of the roller v|51 with the raised portion of the cam |4| re sults .inr a clockwise movement of the arm |55 asviewed from the left, hand end of the facsimile machine, thereby imparting a rocking movement to theY spaced members |52 and |53;

Aszthe rocker shaft |54 is rotated as described, the-cradle members |52 and |53 are moved forward until a position is reached whereby the drumror copyholder 84 is permitted to rollrfrom therecesses formed in these members into any suitable receptacleor conveyor. A continuation of the rocking movement brings the upwardly extending arms |58 and |59 respectively of the members |52 and |53 into engagement with the respective detents such as |32. These detents are moved out of the downward path of the arbors such as |3| of the copyholder H9 thereby permitting the copyholder to drop soy that the arbors thereof rest on the upper edges of the arms |58 and |59. When, by continued rotation of the cam |4, the rocker shaft |54 is permitted toreturn the members |52 and |53 to their upright positions under the iniiuence of a spring convenientstationary member, the upper. edges of the arms |58 and |59 are withdrawn from under the arbors of the copyholder Il@ thereby allowing theseearbors to roll into the recesses formed in the cradle members. holder H9 is thusr carried into a position such that when the members |52 and |53 have been fully restored to their upright positions, the in.-V

dentations formed in the'endsofthe arborel may bey engaged by the coni-cal Y centering points formedY on the shafts 88 and 89. Prior to this engagementthe axis of the copyholder as it rests in the recesses of the cradlemembers, lies rslightly below the center of rotation provided by the centering shafts. Hcwever, because of the conical configuration of the ends of thesev shafts, the sub'- sequent movement of the rod 59 toward the copyholder is instrumental in lifting. the copyit may rotate freely.

drum changing cycle just described is effected by applying power to the motor. |34 subsequent toa scanning operation, or at any other desired time, by means which will be described more lfully in the of the specification. A cam is mounted Y.on the cam shaft |38 for cooperation with a movable contact memberi3. The cam l|62v is oriented with respect to the cams i3d and: |4| so that,` atvthe completion of a drum changing cycle, the

The initiation of the vand to any ff The new copyv Operation port-ion evo gontactflftais moved out of engagement with ai 7 5I Central station transmitting apparatusv A preferred form of transmitting apparatus to be usedvin the facsimile system comprising the invention is shown diagrammatically in Fig. 6. The mechanical details of one Suchemachine are disclosed and claimed inl Patent No. 2,158,391, granted to R. J. Wise on May 16, 1939. and entitled System and apparatus for facsimiletelegraphy. Only enough of the mechanism disclosed in said patent is shown herein to afford those skilled in the art an understanding of the instant invention. This facsimile machinefalso employs a cylindrical drum or copyholder |65 which is supported for rotation and driven by means of a motor |66 substantially in the same manner as that described in connection with Fig. 5. Afriction clutch |51 is used to permitA the stopping of the driving shaft |63 during idle periods when latch |69 is engaged with a peripheral notch formedr in a disc |11. This facsimile machine, as shown, is-not provided with auto'- matic drum changing facilities although it is contemplated that such an arrangement may be used without departing from the invention. A dead Ycenter or spindle |12 which acts to support one end of the copyholder |65 is urged toward its drum engaging position by a spring |13 attachedV to a radially extending pin |14 at# tached to the spindle and also to any convenient stationary member such as'a bracket |15. When it is desired to remove onedrum from the machine and to place another in position to be scanned, the spindle |12 is manually moved toward the vleft asviewed in this drawing. During this. movement the pin |14' slides in a slot |11 formed in a. bracket member |18. Adjacent the extremity of the angular .bracket |18 are formed two notches |13 on either side of the slot |11. When the spindle |512 is withdrawn a sufficient distance, the pin |14 may be placed in veither of the notches |19 by* giving the spindle i12 a slight twist in either direction. Thus the spindle is restrained in its withdrawn position whilevone copyholderY is being removedfrom the machine and anotherone inserted in its place.

A'carriage` 18| is located adjacent the copy'- holder supporting. and driving mechanism and is provided with a plurality ofV sliding members |32 which. are arranged for movement over a pai-r of rails .|831 A lever |84 is pivoted on the carriage .and arranged to be tiltedf upward or downwardby-.ether a` `spring or-an electromagnetfl-ST whenV the latter is energized. An optical scan-v ning ,device |38 is mounted onfthecarriage' |f8| preferably in the mann-er shown in the Wise patent hereinbefore referred to, but as shown herein at one extremity of the lever |54. threaded split-nut Y |89 is also carried adjacentl this'extremity of the lever so that whenthe lat- |9| may Y Y facsimile scanning |93 will have been moved far enough to the right as viewed in this ligure to permit the engagement of the stylus with a hole or aperture |95 formed in the sheet |94'. This engagement permits the stylus |93 to make a momentary contact with the metallic portion of the drum |35 v'vhichv is at ground potential therebyv applying the ground to the stylus |93 for the purpose of giving' an indication of the` completion of the scanning operation as described more fully hereinafter.

Operation The operation of the facsimile system will now be described in connection with Figs'. 3, 4, 5 and 6 arranged as indicated in Fig. 2. All of the apparatus employed in the system is shown in. its idle condition. Most of the relays used for control purposes are shown deenergized. However, during the idle period a few of these relays are held operated and such relays are so shown on the drawings.

As previously described, the alternating current facsimile signals are transmitted overa pair of line conductorsl L superimposed upon a direct current potential impressed equally upon the conductors. The direct current signaling channel is utilized to perform the various control functions necessary for the operation lof the system. During an idle period the line conductors are maintained at a negative potential with respect to ground. This potential: is Supplied by a negative battery |96 locatedY at the transmitting equipment of Fig. 6A and-k is connected to the upper transfer contact |91 of jack |99. The connection is further extended through a lever spring H39 of the jack and conductor 26|, through contacts 292 and 233 of concentrator relay 20'4 of Fig. 4, back' contact' and tongue 291 of relay 293, the' winding of relay 11, and' con-l ductor 15 to the midpoint ofthe inductance T4'. f-

This simplex signaling circuit is completed at the branch ollice of Fig. 3' through the winding cf the polarized relay 64, a resistancer2ll5, back contact and tongue 2'I'I of a relay 2f|2'. 'l'.hel current ilowing inthe circuit just described is lim- .ited to a relatively low' value by the resistance 209 so that concentrato'r relay 11 is insufficiently energized to operatev its tongue to the front contact.

When the branch office desires to transmit' subject matter to the central office a sheet 3'6" containing the subjectmatter is mounted on the cylinder 31 as described. This sheet is applied to the drum so that the' lap 213i which is formed therein bears a delinite relation to a short' irisulating segment 2If4 of a disc' 2|5a When the' branch cnice transmitting equipment is thus made ready the send-receive switch 53 is p'ositioned on its left hand contactsv as shown connecting the line conductors L through blades ifi? and 2|1 and their respective left hand contacts to the output of the transmittingr amplifier 213, the input of which is connected to the scanning device 49. `The start switch 3| is moved to its right hand contact thereby connecting the ala negative battery ternating current potential 62 to the substation apparatus;

The primary winding 2|9 of a transformer 220' is energizedfrom the alternator'v 62 throughv an obvious circuit. Thus', voltage is applied to the filament' or cathode heating device 22| of a rectifler 222. Also the alternating ,current is connected to' the heating 'elements' of both the' transmitting and receiving amplifiers 2|8 and 223 respectively. One such heating element`224 of the tube 226` is shown.. The primary winding 221 of a' filament transformer 228" is energized by a circuit which may beitraced from one side ol' thealternating current suppl'ytc'Z through the switch 6| and its right hand contact, conductors 223` and 23|, winding 221, conductor 232, and switch blade 233 and its left hand contact tc the other side of the alternating current supply. Thus the secondary winding 234 of transformer 228 becomes energized by induction to supplyp'otential to the scanninglamp' 5|'. The connection of alternatingl current to Vthe* conductors 2'29 and 236 results in the starting of the' driving motor 39 and the light chopper' motorwhich is housed in the scanning device 49.

The startingA of the motorl 39 initiates rotation of the cylinder' 31` and the feed screw 42 thus conditioning the ,facsimile scanning apparatus for operation as soon asv the desired connection has been made to the central station and other preparations which will be subsequently dcscribed have been made. Itwil'l vbe noted that the simplex signalingY circuit` is permanently connected to ground as long as .relay 2|2' remains unenergized regardless of the periodic engagement of brush 231 with the' insulating segment 2|4`.

Since the tongue 2381 of 'the polarized relay '64 is positioned onV its upper Contactin response to the negative potential applied to the simplex sige naling circuit, relay 239' is operated bythe closure' of the switch 6|". Subsequent to its oper'- ation this relay is locked in this position through its tongue 24| in cooperation with its front con- The operation of relay `239 closes the tongue 242 against its front contact thereby short circuiting the resistance 209,. one terminal of which is connected to the tongue 242' and the' other terminal of which is connected through the switch blade 243 and its lefthand." Contact' to the front contact of relay 239 which is associated with the tongue 242. The short circuiting of resistor 209 produces an increase in thev current of the simplex signaling circuit'. The increased value of the signaling current constitutes a calling signal which istr'ansmitted tothe concentrator switching equipment- Relay 1'1 of Fig. 4 responds to the relatively high value of current flowingin the simplex circuit to operate its tongue 244 to its front contact thereby operating relay 204.V The operationof this relay effects engagementy between tongue 245 and contact' 203 which applies-the negative potential supplied to conductor" 241.,by 248 totlre simplex circuit and', at the same time, disconnects' from this circuit the potential originally supplied .by battery |96 of Fig. 6. The closure of tongue 249 of relay 204 on its front contact operates a gaseous conduction device such as =a neon lamp 251 which is located adjacent jack |98' for the purpose of indicating that the line associated With this'` jack is busy. The operation of contact' 252 of relay 234 to its front contact. applies aground through.

the tongue 253 and back Contact of'relay' 238 to a conductor 254. The application of ground to this conductor is for the purpose of bidding for connection to one of the central ofiice recording machines and may be made from any unit of the switching apparatus. There is shown in Fig. 4 a portion of the switching apparatus associated with another branch oilce signaling channel and it is assumed that the transmitterassociated therewith is operatively engaged with one of the central oice recorders. relay 251 is positioned on its back contact so that the ground applied to conductor 254 is further transferred to` tongue 258 of relay 259 which is similarV to relay251 but, being associatedwith switching equipment which is idle and with a recorder which is in condition to receive, the tongue is positioned on its front contact, whereby the ground originating at tongue 252 of rel-ay 204 is applied to relay 26| causing its nneration. Y

The energization of relay 26| causes the engagement of tongue 262 with its front contact thereby energizing thev operating winding of a dash pot relay 263.v The mechanism associated with this relay is timed so that the bridging member 264 isnot effective to close the contacts associated therewith for a predetermined period of time. The purpose of this arrangement is to provide a guard against faulty operation of the switching equipment whereby, if the desired connection is not completed within said predetermined time, certain alarm facilities are actuated bythe voperation of this relay and will be discussed in greater detail in a later portion of this specification. Another tongue 266V o1" relay 26| prepares a circuit through its front contact forY the operation of a lamp or other visual signal 261 if the bridging member 264 of relay 263 closes its vassociated contacts while relay 26| is energize'd- .TheV operation'of relay 26| also prepares a circuit for the operation of the stepping switch Thus, tongue 256 or".

69 to locate the channel connected to the calling This circuit may be traced from the negative potential of conductor 241 through the operating coil 268 of the stepping magnet, interrupter contacts 269; conductor 21|, tongue 212and front contact of relay 26|, back contact and tongue 213 of relay 8|, to the wiper 214 of the stepping switch. When the wiper is in contact with any of its studs such as 216 which is associated with another communication channel, the circuit for the operating winding-268 is completed to ground irrespective of whether the second channel is busy or idle. If the channel is busy, ground lis applied to the contacts of all of the stepping switches corresponding to stud 216 ofthe switch 69 by the engagement of tongue 211 of relay 218 with its front contact. If the channel is idle, relay 219 is deenergized and the ground is applied to the stepping switch contacts by the engagement of tongue 29| with its back contact;V Hence engagement of the stepping switch wiper 214 with a contact stud associated with any of the channels other than the one calling for connection results in the movement sub-station.

of the wipers of the stepping switch 69 to the next. adjacentv studs. The stepping switch is provided with the usual interrupter mechanism including an armature 282 for the purpose of momentarily opening the contacts 269 whenever the winding 268 is energized. When Ythe wiper 214 reaches the contact stud 283 which is the one associated with the calling sub-station, the circuit for the operation of the stepping magnet 268 is open, since relay 204 is energized thereby disconnectingr the ground connected to tongue 252 from the contact stud and since relay 208 has not been operatedat this stage thereby leaving the ground connected to its tongue 284 disconnected from the contact stud. Thus, further stepping of the switch 69 is prevented.

A second conduction path through the stepping switch operating winding 268 is provided through the operating Winding of relay 8|, the front contact and tongue 286 of relay 26|, conductor 231, to the normally closed contact 288 of a push button 289, and back contact anditongue 29| of relay 292 to ground. This circuit is established all during the time that the stepping switch 69 is operating but as long as the wiper 214 is connected with a ground, the winding of relay 8| is short circuited. However, as soon as the wiper 214 becomes engaged with contact stud 283, the short circuiting ground is removed, permitting the operation of relay 8|. This relay is then locked to the ground of tongue 29| of relay 292 through its tongue 293 and associated front contact and remains in this condition for the remainder of the connection of the sub-station to the central oiiice recorder. The current necessary for the operation and locking of relay 8| is insu'icient to cause further operation of the stepping switch.

As soon as the relay 8| is operated, the ground connected to the front contact associated with tongue 213 is applied to the stepping switch wiper 214 which transfers it Ato contact stud 283 and corresponding ones on all other stepping switches, thereby preventing any of the other stepping switches from stopping in this position. The engagement of wipers 18 and 19 with the respective contact studs 61 and 68 andthe engagement of tongue 294 of relay 8| with its front contact connects the line conductors L through the amplifier 82 and the signal inverting apparatus 83 to conductor 296 which is connected to the recording stylus I3 of the facsimile machine of Fig. 5. Thus, it is seen that the desired connection has been made between the calling substation and the recording apparatus of the central oice.

The operation of tongue 291 ofV relay 8| to its front contact connects a ground through wiper 298 and contact stud 299 of the stepping switch 69, through the front contact and tongue 30| of relay 204 to the winding of relay V2|J8 which results in the operation of this relay. The connection of the tongue 253 of this relay with its front contact locks the relay in its operative position. Also tongue 284 applies a ground to the contact stud 283 of the stepping switch thereby busying it to al1 other stepping switches. The disengagement of tongue 253 of relay 208 from its back contact removes the ground of armature 252 of relay 294 from conductor 254. Y

tongue 262 is connected to the front contact associated with the tongue 362 of relay 8| which in turn is connected to the negative potential of conductor 241. This arrangement permits the continued energizatlon of relay 263.

The disengagement of tongue 293 of relay 8| from its back contact deenergizes relay 259 permitting its tongue'258 to be restored to its back contact, thereby transferring the answer-next circuit to a higher numbered recorder and preventing calls arriving during the operative condition of the unit of the switching apparatus being described from operating such equipment. Relay 259 is of the slow-to-release type so that, even though it is deenergzed at substantially the same time that relay 208 is energized, it does not release its armature 258 until the ground originating at tongue 252 of relay 204 has been disconnected from the conductor 254. This arrangement prevents the possible erroneous operation of another stepping switch corresponding to switch 69 which will happen if the answernext circuit is transferred to another recorder with a ground still connected to the conductor 254. Of course, in the case of another sub-station waiting for connection to a recorder, the transfer is made under these circumstances, but the subsequent operation of the other stepping switch is normal.

A relay 303 having two operating windings 304 and 30B, one terminal of each of which is connected to the negative potential of conductor 241, is maintained in an operative condition during the switching operation just described by the connection of a ground to the other terminal of winding 306 through the back contact and tongue 301 of relay 308. Following the operation of relay 208 the ground connected to tongue 244 of relay 11 is extended through the tongue 300 and front contact of relay 208, contact stud 3|| and wiper 3|2 of the stepping switch 69, tongue 3|3 and front contact oi relay 8| and tongue 3|4 and front contact of relay 303 to the winding 304. This ground is also applied to the winding of relay 300 causing the operation of this relay, which open the circuit through the winding 305 of relay 303. But this relay is maintained in its operative condition by the energization of its winding 304.

Also, when relay 208 is operated the simplex signaling circuit, which is connected to tongue 201 of this relay, is switched to the front contact associated with this tongue for connection to the positive potential which is supplied to conductor 3|6 by a battery 3|1. Thus, the potential applied to the simplex circuit is reversed from negative to positive thereby constituting a signal indicating to the sub-station apparatus that the desired connection has been made.

l The positive simplex potential applied to the polarized relay 04 of Fig. 3 effects the movement of the tongue 238 to its lower contact thereby connecting one terminal of the alternating current power supply E2 to the front contact associatedwith tongue 3|8 of relay 2|2. It should be noted that following the reception of the calling signal at the central station, the resultant switching operations initiated thereby are normally completed in a very short time so that the simplex signal transmitted from the central station to the sub-station indicative of the completion of the switching operation will normally be received at the sub-station before the thermionic rectier and amplifier have had an opportunity to become operatively conditioned. However, as soon as rectifier 222 and the amplifier 223 have been properly conditioned for operation, the plate current which is supplied to the tube 226 is conducted through relay 2 |2 thereby operating the tongues 2|| and 3||3 to their respective front contacts.- The engagement of tongue 3|8 with its front contact connects one side of the alternating current supply through conductor 3|9 to one terminal of an electromagnet 32|, the other terminal of which is connected to the opposite side of the alternating current supply through switch 6| and its right hand contact. The energization of electromagnet 32| moves the split-nut 41 into operative engagement with the feed screw 42` thereby initiating the scanning function of the sub-station transmitting equipment. The disengagement of tongue 2| of relay 2| 2 from its back contact removes one ground connection from the simplex circuit which-,is thereafter extended through Aconductor 322 .to brush 231 and to the ground connected to brush 323 when the brushes are both in contact with the conducting Vportion of the disc 2|5. On the first revolution of the disc 2 5 following thel operation of relay 2|2, when the brush 231 is in contact with the insulating segment 2 I4, the simplex circuit is momentarily interrupted. 'I'he interruption of the simplex circuit constitutes a phasing signal which is transmitted to the central station apparatus for the purpose of initiating the scanning function of the recording apparatus.

The interruption of thesimplex circuit deenergizes relay 11 of Fig. 4, permitting the armature 244 to leave its front contact thereby momentarily opening the circuits controlled thereby. The momentary opening of the circuit through relay 204 is ineffective to release the armatures of this relay because of the fact that this relay is of the slow-to-release type and is designed to remain operated during the short time that the simplex circuit is opened by a phasing signal. However, the interruption of the circuit through winding 304 of relay 303 permits the armatures of this relay to move to their respective back contacts. Relay 308 is also of the slow-to-release type and is unaffected by the momentary interruption of its operating circuit. Thus, it is seen that when the armature 244 of relay 11 re-engages its front Contact, relay 303 remains unoperated since the circuits through both of its operating windings are incomplete.

The disengagement of tongue 324 of relay 303 from its front contact removes the ground from conductor 320, resulting in the release of relay 321 of Fig. 5f. 'I'he engagement of tongue 328 of this relay with its back contact operates relay 329, the disengagement of the armature 33| of which from its back contact releases relay 333. The restoration of tongue 334 of relay 333 to its back contact opens the circuit of electromagnet thereby permitting the lever I 2 to be pivoted so that the split-nut ||4 becomes engaged with the feed screw ||B and the stylus ||3 is moved into engagement with the surface of the recording sheet |04. Engagement of tongue 33| 'of relay 329 with its frontl contact completes a circuit through the winding of the electromagnet |03. Thus, the latch |0| is disengaged from the notch of the disc 99 permitting rotation of the cylinder 84; This completes the necessary arrangements for effecting the scanning function of the recording apparatus. It will be noted that the oper"- ations just described are initiated by the engagement of brush 231 with the insulating segment 2|4 at the branch station so that the respective scanning functions at the branch transmitting station and the central recording station occur substantially simultaneously.

Normally, the central office recorder is permitted to run until released by the branch office. When the branch office transmitting equipment has finished scanning the subject matter, the

:incasso switch 6| is moved'to-its left hand contact. 'Ihe operation of Athis switch may be manual or automaticas desired. One device for automatically restoring this switch toits idle position is shown inthe Wise, Vet al. application, Serial No. 293,188. The branch ofice equipment is thereby restored toits idle condition. i The Ydisengagen'ient vof tongue '242 of relay'239 from its front contact removes the short circuit from 'the resistance 209 thereby reducing the'value of the simplex signaling current. lAs previously described, this relatively small Value of lcurrent is insunicient to maintain the operation of relay 11. Hence relay 204 isreleased, thereby releasing relay 288. The movement of tongue 201 of relay 208 to its back contact applies negative `'potential to vthesimplex circuitwhich is effective at the sub-station to move tongue 233 of relay 64 to its upper contact. 'l The release ofrelay 11 also results in the restoration or tongue 301 of relay 308 to its back contact, thereby completing a circuit through Winding 336 of relay 303. This relay becomes operated to connect the ground of tongue'324 to conductor 326, thereby operating relay 321 of the recording apparatus. Thus, relay 329 is released to deenergize the electromagnet |03, allowing thelatch A to be reengaged with the peripheral notch of disc 99 and to operate relay 333. The operation of this relay energizes the electromagnet which disassociates the recording stylus H35and the split-nut H4, respectively, from the recording sheet |04 and the feed screw H6. The retractile spring |18 becomes effective to move the carriage |08 to its extreme left hand position;

"The engagement of tongue 328 of relay 321 with its `front contact ycloses a circuit through winding336 of relay 331, which circuit is cornpleted Vthrough a condenser 338. The current which flows in this circuit to charge the condenser issutcient to cause `the operation of relay 5331, which is then locked through its tongue 339 and front contact. The steady state current which is permittedto ow through winding 335 through .a relatively high resistance 34| is insuf- Vficient to maintain the relay in its operative condition,'but it is seen that at this time the relay is locked through an auxiliary winding 342. The engagement of tongue '339 of relay 331 with its front contact closes a circuitto operate relay 343; The operation of tongue 344 of this relay to its front'contact connects a source of potential 345 tothe drum changing motor |34. Thus,is initiated the drum changing cycle previously described. At the completion of this -cycle contacts |93^|64 are openedby the cam |32 thereby interrupting the circuit through the Winding 342 of relay 331, which causes the relay to be released.` Relay A343 also releases to open the circuit through the motor |34.

vProvisions are made for disabling the concenN trator apparatus during a recorder drum changing'cycle. As long as the recorder contact 346 is -closedia'nd the armature 341 of relay 331 is engaged with its back vcontact,`winding 348 of relay 292^is short circuited. But when relay 331 is operated to initiate' a drum changing cycle, Winding 348 of relay 292 becomes energized through a resistance-349. The movement of the tongue 29| of this relay from its back contact opens the` locking circuit for relay 8| at the concentrator, thereby permitting the tongues of this relay to .be moved to their respective back contacts. It

also prevents the operation of relay 259 since the circuit through its Winding stands open at CII the back contactv associated with tongue 29|. Thus, during the drum changing cycle oft-herecorder the Vswitching equipment associated there.- with is restored to normal and means are provided for preventing a call from being received by this unit of the concentrator equipment. if, at the completion of a drum changing cycle, when armature 341 of relay 331 is restored to its back contact, a fresh drum is Ynot placed in the recorder, the spindle 89 is permitted to move iar enough toward the right to open contact 343 by means of a pin 35|. Consequently relay 292 `remains operated thereby disabling the switching equipment until such time as the recorder is furnished with a fresh drum. However, duringnormal operations the machine is providedwith an additional copyholder and relay 292 is released after each drum changing cycle. Relay 259 becomes energized when tongue 29| of relay 'V292 re-,engages its back contact and moves its tongue 258 to its front contact, thereby conditioning the switching equipment to accept another call.

The recording apparatus is provided witha manually operated push button 352 by Awhich winding 342 of relay 331 may be energizedto initiate a drum changing cycleV independently of controlsignals from the sub-station transmitter. Onepurpose of this facility will be pointed out in a subsequent portion of the speciiication.

In operation of the system, the apparatus of Fig. 6 transmits copy from the central station to any sub-station. A sheet |94, containing the subject matter to be transmitted, is placed upon a drum |85 which is placed in the facsimile transmitter as shown on this drawing. A plugl353 is inserted in the jack |98 which is associated with the circuit connected to the desired branch oice. The tip 354 and sleeve 356 of the plug are .connected respectively to corresponding contacts 351 and 358 of the jack and then by `means of conductors 359 and 36|, respectively, to the `line conductors L. The simplex signaling vcircuit connected to the lever |99 of jack |98 is transferred from its connection to the negative battery |96, made through transfer contact |91, to a transfer contact 382 from which it is further extended by means of the ring connection 333 of the plug 353 through a closed transmitter contact 364 and winding of relay 383 to the positive potential of battery 361. It is assumed that, at thecentral office transmitting apparatus, motor |86 is supplied with power to drive the transmitting apparatus and the latter is consequently conditioned for operation.

Prior to the energization of relay 368 bythe insertion of the plug 353 into the jack |98, relay 388 is operated by the engagement of the armature 369 of relay 31| with its back contact. Accordingly, the armature 312 of relay 388 is con nected with its front contact to operate relay 313 of relay 313 which is supplementary to the -one applied by the armature 312 of relay 338. vThe movement of armature 339 of relay 31| to its front Contact deenergizes relay 338 which releases its armature 312 to engage its back contact. It will be noted that, prior to the opening of the original operating circuit for vrelay 313 by the release of relay 338, a second operating circuit is completed by the operation of relay 363. The connection' of the positive potential of battery 361' through the winding of relay 366 to the simplex signaling circuit constitutes a calling signal which is transmitted to the branch oifice of Fig. 3.

Reversal of the simplex signaling potential from negative to positive causes the armature 238 of polarized relay 64 of Fig. 3 to be moved to its lower contact thereby connecting the alternating current source 62 to a bell 63 or equivalent signal. This signal may be replaced or supplemented by a visual signal to attract the attention of the substation attendant. In response to the simplex signal indicating that the central oice desires to transmit subject matter to the branch office, the attendant at the latter station places a sheet 36. of recording material on the drum 31 of the substation apparatus. The send-receive switch 59 is moved to its right hand contacts and the start switch 6| is moved to its right hand contact. Signal 63 is silenced and the alternating current potential is applied to the facsimile apparatus as previously described. However in this instance the `relay 239 is not operated since the operating circuity therefor is open at the upper contact of relay 64. Also the resistance 269 is not short circuited since the circuit therefor is open by the disengagement of switch blade 243 from its left hand contact. Accordingly, the simplex signaling current is maintained at its lowv value. The line conductors L are connected by switch blades 2|6 and 2|1 and their respective right hand contacts tothe receiving amplifier 223, the output of which is connected to the recording stylus 54, The system is now in condition for operation as soon I as the rectiiier 222 and the receiving amplifier 223 become operatively conditioned.

The operation of relay 2|2 in response to the heating of the rectifier and the receiving amplier transfers the simplex signaling circuit to the brush 231 from which the phasing impulse is transmittedin the manner previously described.v

By the operation of tongue 3|8 of relay 2|2 to its front contact the alternating current is applied to the electromagnet 32| by which carriage feed is effected. In addition, the operation of this relay armature connects the alternating current potential. to conductor 318, which is connected through bladeV 319 of switch 59 and its right hand. contact to the electromagnet 58. The energization of this electromagnet depresses thelever 56, thereby lowering the recording stylus 54 into contact with the sheet 36.

The phasing signal which is transmitted from the branch office is received at the central oilice transmitting apparatus of Fig, 6 and results in the deenergization of relay 366. The operating circuit for relay 313 is thus interrupted permitting the armatures of this relay to be moved to their respective back contacts. The facsimile signals which are generated by the scanning device !88 are connected by a pair of conductors 38| to the input terminals of an amplifier 382. One of the output terminals of this amplier is connected by conductor 583 directly to the tip terminal of the plug 363 through which connection to one of the line conductors L is made. Following the release of the armatures of relay 313, the other output terminal of the amplifier is connected by conductor 384 through the back contact and tongue 389 of relay 313 and the back contact and tongue 381 of relay 388 to the sleeve terminal 356 of the plug 353 from which it is transferred to the other of the line conductors L. The disengagement of tongue 389 of relay 313 fromits front contact deenergizes relay 39| permitting its armature 392 to be moved from its rfront to its back contact. The disengagement of this armature from its front contact deenergizes the electromagnet |81 thereby allowing the spring |86 to pivot the lever |84 so as to engage the split-nut |89 with the feed screw |9| and to move the stylus |93 into registry with the surface of the sheet |94. The scanning apparatus |88 is'thus moved into operative position relative to the subject matter to be scanned. The engagement of tongue 392 of relay 39| with its back contact energizes'the phasing electromagnet 393 which disengages the latch |69 from the i disc |1| thereby permitting rotation of the driving spindle |68 to rotate the drum |65. In this manner the scanning function of the transmitting apparatus is initiated in response to the phasing signal transmitted from the branch ofiice recorder. The release of armature 394 of relay 323 to its back contact connects the ground of armature 312 of relay 368 to one terminal of the winding of relay 313 so that, upon the reoperation of relay 366, immediately following its release because of the short duration of the phasing signal, relay 313 is not reoperated, its winding being short circuited. This condition is made possible by the character of relays 31| and 368 both of which are of the slow-to-release type and are unaffected by momentary operations of the armature 316 of relay 366.

After the scanning operation has been completed and the carriage |8| is moved sufliciently toward the right hand limit of its travel, the stylus |93 engages the opening |95 in the sheet |94 to apply a ground to the winding of relay 368. This relay then` operates and locks through its tongue 396 and its front contact and the tongue 392 and back contact of relay 39|. A signal 391 is also actuated to call the attention of the attendant to the fact that the scanning operation has been completed. Also; the facsimile signaling circuit is opened by the disengagement of armature 381 of relay 388 from its back contact. The attendant then withdraws the spindle' |12 to remove the cylinder |65 from the facsimile transmitter and also removes the plug 353`from the jack |98. The withdrawal of the spindle |12 opens contact 364 and closes contacts 398 and 399. Either the opening of contact 364 or the removal of the plug from the jack releases relay 366, the tongue 316 of which is released to its back contact, thereby short circuiting the winding of relay 31|. The armature 369 of this relay is restored to this back contact to energize the winding of relay 368. The movement of the armature 312 of this relay from its back contact removes the short circuit from the winding of relay 313 and the engagement of the armature with its front contact closes an operating circuit through the winding of relay 313. The disengagement or armature 386 of relay 313 from its back contact opens the facsimile signaling circuit at a second point. The closure of contact 398 by the withdrawal of the spindle |12 energizes the winding of relay 39| which locks through the tongue 389 and the front contact of relay 313. The operation of relay 39| unlocks relay 388, thereby silencing the signal 391 and partially reclosing the facsimile signaling circuit through armature 381 and its back contact. The movement of tongue 392 of relay 39| from its back to its front contact deenergizes the electromagnet 393 which releases the latch |69 to reengage the notch in the .disc thereby stopping `rotation of the drum |65, and also energizes the electromagnet |81 which moves the scanning device |88 and the stylus |93 from their the simplex signaling potential from positive to negative operates the tongue 238 of relay 64 to its upper contact which causes the operation and subsequent locking of relay 239. Despite the closure of armature 242 of this relay on its front contact the resistance 209 is not short circuited since the lever 243 of switch 59 is engaged with its right hand Contact. Hence, there is no response of any of the concentrator switching apparatus to the operation of relay 239.

However, it is to be noted that in series with winding'A 40| of transformer 220 and the heating element 22| of the rectifier 222 is a lamp 402. Prior to the operation of relay 239 this lamp is short circuited by the engagement of armature 403 and back contact of this relay and right hand contact and blade 404 of switch 59. When the tongue 403 is disengaged from its back contact, the'short circuit is removed thereby permitting the lamp 402 to be lighted. This is an indication to the attendant at the branch oil-ice that the transmission from the central oiice has been completed and that the sub-station apparatus may be disconnected. The shutting down of the branch oiiice equipment may be effected by moving the switch '6| to its left hand contact thereby disconnecting the alternating current power source 62 from the equipment or means may be provided on the facsimile apparatus in accordance with the disclosure of the co-pending application of R. J. Wise et al. Serial No. 293,188 whereby the switch 6| is moved to its left hand contact automatically at the end of the scanning operation.

Special features The facsimile system disclosed herein is provided with a number of special features designed to insure the correct manipulation of the branch oice apparatus and to insure the complete transmission of messages. Branch offices are usually staffed with attendants who are not trained operators of the telegraph equipment and consequently cannot be relied upon to invariably follow a fixed operating routine. Also it has been found that in some circumstances the desired connections between a calling substation and a central office recorder may not bev made as expeditiously as some of the equipment is designed to normally operate. Such a condition may arise when all of the central oice re scanning function at the branch office until a connection has been made to a central oflice recorder regardless of the length of time it may take to establish sucha connection. Numerous other possibilities for the loss of messages by transmission from a branch office without a recorder being properly connected to receive the transminssion are guarded against by suitable apparatus and circuits and will be set forth in detail in the following description of said apparatus and circuits.

If al1 of the central oiiice recorders are busy when an additional call is initiated at another sub-station, the call is stored at the concentrator and the sub-station apparatus is prevented from transmitting until a connection has been established with a central office recorder. The operation of the switch 6| of Fig. 3 results in the operation of relays and 2040i Fig. 4 as described. But, since all recorders are busy, the answer-next circuit is not connected to any of the relays such as 26|. Hence, the connection of the ground of tongue 30| of relay 204 to conductor 254 is ineffective at this time to cause the operation of oneof the stepping switches such as 69. Before one of the central olice recorders becomes idle so that the normal switching operations may be completed, the sub-station apparatus may have sufficient time to become operatively conditioned. As described previously, relay 2|2 of Fig. 3 then operates to remove the permanent ground from the simplex circuit and permit the transmission of interruptions from the phasing commutator 2| 5. These interruptions, one of which normally constitutes a phasing signal, cause momentary releases of relay 71 of Fig. 4 but are not repeated thereby to the phasing apparatus since thel switching operations are incomplete. Also, the operating circuit for the split-nut magnet 32| of Fig. 3 is extended through the armature 3|8 and front contact of relay 2|2 to the lower contact of relay 64. However, since the polarity of the simplex signaling current is still negative, armature 238 of this relay is held on its upper contact, thereby preventing the energizing of the magnet 32| and the initiation of the scanning function of the sub-station transmitter.

As soon as one of the central office recorders is released and supplied with a fresh recording blank, the concentrator relay 259 of Fig. 4 associated therewith is operated to connect the answer-next circuit to relay 26|. The switching apparatus then operates to connect the calling sub-station with the recorder as described. The operation of relay 208 reverses the polarity of the simplex signaling current from negative to positive, thereby moving the armature 233 of relayv 54 `of Fig. 3 to its lower contact to start the scanning function of the sub-station transmitter. The flrst of the interruptions transmitted from the phasing commutator 2|5 after the completion of the switching operation operates the central oice phasing apparatus as previously described.

One feature which is also described in detailV in the Wise, et al. application, Serial No. 293,188 is provided at the branch office where relatively unskilled operators are often in attendance. In addition to mounting the appropriate sheet on the cylinder 31 of the machine, the branch office attendant must manipulate switches 59 and 6|. Depending upon whether the apparatus is to be used for sending or receiving the switch 59 is positioned respectively on its left hand or right hand contacts as described. Also, by reason ofV t the different conditioning of the simplex circuit under these two operating conditions, the switch 59 and the armatures of relay 239 must bear a definite relationship to one another. In order to insure that this relationship is invariably established, the lamp 492 in series with the winding 49| and the heating element 22| is employed. When the relationship is correct, the lamp is short circuited by the tongue 493 of relay 239 and either of its contacts in cooperation with blade 494 of switch 59 in cooperation with its respective contacts. An incorrect relation between these two devices results in the lighting of the lamp and, because of the resistance thereof, the heating element 22| of the rectifier 222 is insuiciently energized to allow the rectifier to function. Thus the apparatus is arranged so that a signal is actuated to warn an attendant of an incorrect relationship between the switch 59 and the relay 239 and it is impossible to operate the branch office apparatus until this relationship is correctly established.

It has been seen that the concentrator switching equipment which is associated with one of the central oflice recorders is prevented from receiving a call from a branch ofce during the time that a drum changing operation is occurring at the recorder. Also, if at the completion of a drum changing operation, a fresh drum is not placed in the recording apparatus, the switching equipment' is continued in its disabled condition. Until the concentrator relay 259 is operated to switch the answer-next circuit to the winding of relay 26|, the unit of the switching apparatus shown in Fig. 4 is prevented from receiving a call from any of the branch orlices. Relay 259 may not be operated until armature 29| of relay 292 is engaged with its back contact. As described, this relay is energized to attract its armature to its front contact during the drum changing operation by the disengagement of tongue 341 of relay 331 from its back contact. At the completion of a drum changing operation the tongue 341 is moved to its back contact by the deenergization of relay 331, but if a fresh drum is not installed in the recording apparatus, the spindle 89 is permitted to move toward the right a sufcient distance to open the contact 346. The opening of this contact maintains the relay 292 in its operated condition, thereby preventing the operation of relay 259. This unit of the central oiice recording apparatus remains in a disabled condition until the recorder storage magazine is supplied with one or more fresh copyholders and the push button 352 is depressed to insert one of the stored copyholders into the recorder as described. Following the drum changing cycle in which the fresh drum is installed in the recorder, relay 292 releases to operate relay 259 thereby rendering the recording apparatus receptive to another branch office call.

It may be that for some reason after a branch oilice call has been received at the concentrator apparatus and the desired connection to a recorder made, the recorder carriage |98 does not start to feedl within a predetermined time, such as 40 seconds for example. The concentrator relay 263 is adjusted to move the bridging member 264 into engagement with its associated contacts at the end of this predetermined time. A circuit is thus closed from the ground connected to one of these contacts through conductor 496, a closed contact 401 and the winding of a relay 408 to the source of potential 345. This relay operates and locks through armature 499 and its associated front contact, and contact 4I| of the push button 289. Armature 4|2 applies a ground through itsr front contact to short-circuit winding 348 of relay 292. The disengagement of armature 4|3 from its back contact opens the operating circuit through winding 4|'4 of relay 292. Thus, this relay is prevented from operating, thereby holding the concentrator relay 8| locked in its operated position. 'The central office switching apparatus is therefore maintained in its operated condition with the wiper contacts of the stepping switch 69 engaged with the contact studs associated with the calling branch oice. The purpose of locking the call in the concentrator equipment is to enable an attendant to refer to the number of the position of the stepping switch 69 so that the identity of the calling substation may be established, and the appropriate steps taken to notify the branch ofce that the subject matter transmitted has not been received. Thus, the branch office may be given another opportunity to transmit the message to the central ofce.

In addition to locking the call in the concentrator as described, the operation of relay 498 moves its armature 4|5 to its front contact to hold relay 321 operated even though subsequently the. concentrator relay 393 may be released. Inl this way the scanning function of the recording apparatus is prevented from being started asynchronously and a drum changing operation is not effected. However, if the phasing signal has been received by the concentrator apparatus to release relay 321 but has been ineffective to initiate scanning by the recorder, this relay is reoperated to start a drum changing cycle. In either case, control of relay 321 is taken away from the concentrator apparatus. I

The operation of relay 498 also completes a circuit through armature 499 and contact 4|| of the push button 289 to a signal 4|6by means of which the attention of the central officey attendant may be attracted. The operation of this signal is an indication that the apparatus is not functioning correctly. The attendant may then refer to the recording machine to determine whether or not a drum changing operation Vhas been started, and if not may then refer to the concentrator equipment where the calling substation may be identi-ned as described. After correcting the trouble the central office equipment may be restored to normal by depressing the push button 289. The opening of contact 4|| releases the alarm relay 493 and restores the circuits controlled thereby to their normal conditions. The opening of contact 298 of this switch opens the Alocking circuit through relay 8| thereby releasing the concentrator apparatus and restoring it to its normal condition in readiness to accept another call.

It may be that the substation call is properly received and the recording apparatus started in response to the phasing signal transmitted from the branch oce. However, the facsimile signals may be interrupted during the transmission of the subjectmatter. The facsimile circuit is tested for the presence of the facsimile tone or alternating current signals at a predetermined time after the transmission of the phasing signal. Thispredetermined time is chosen so as to occur after the transmission of the subject matter appearing in the date line of the message. Another of the concentrator relays 4.!1 is connected to the amplier 82 at some convenient point such as in the output of an intermediate stage and is therefore responsive to the facsimile tone. As long as this tone is being receivedfthe armature 4|8 of this relay is attracted to its front contact, thereby energizing the winding of avsloW-to-release relay 4|9. This latter relay is of the slow-to-release type so that momentary interruptions of its operating circuit due to the reception of-facsimile signals representative of Vdarkened portions of the subject matter being .transmitted do not effect the release of its armature 42|. The armature 42| of this relay is thus held out of engagement from its back contact. The predeterminedtime for testing the facsimile signals may be selected While a marginal portion is being scanned, although-substantially any other time has been found to be satisfactory. At that time the carvvriage |08 of the central ofce recorder will have started to move toward the right thereby allowing a Contact arm 422 to also be moved toward the right by a spring 423. The contact arrangement is such that after the carriage has moved a distance sumcient to record the date line of the message, a contact 424 is closed. Also while the marginal or other prearrangedportion of the transmitted subject matter is being scanned, a pair of brushes 426 are bothrin contact'with a conducting segment 421 of a disc 428 attached to the driving spindle 88. If no tone has been received for a continuous period immediately preceding this time and sufficiently long to permit the deenergization of relay 4|9, armature 42| of this relay is engaged with its back contact to apply a ground to conductor 429. This ground is further extended bythe engagement of the brushes 426 with the conducting segment 42,1,V

through the closed contact 424, the closed contact 401 to the winding ofV relay 438, thereby operating this relay.

The operation of relay 408 actuates the signal 4|6, locks the concentrator equipment in position by the disabling of relay 292-and energizes the winding of relay 321 which in this instance is released since the phasing impulse had been previously received to start'the scanning function of the recording apparatus. The operation of this relay restores the recording apparatus to its idle condition and operates relay 331 to start a drum changingy operation as described. The calling subscriber may be identied from the recorded subject matter appearing on the sheet |84 or Aif the facsimile signals failed prior to the reception of the rst part of the message, the subscribers identity may be established by having reference to the stepping switch 69 as described. After the necessary repairs have been made, the push button 283 is depressed to restore the apparatus to its normal idle condition and the subscriber may be notified to retransmit the message Which was not properly recorded. It is obvious that the retransmission of the message in this or the previously described case may be recorded on any of the central ofiice apparatus including that in which the failure occurred, providing, of course, that it is restoredrto an operative condition.

In either of thedescribed cases involving the operation of relay 488 in response to a failure of the system to operate properly, normal function-j ing of the apparatus causes the contact 401 to be opened by the continued movement of the recorder carriage |88 to the right. The timing of the Various apparatus is arranged so that, normal1y,'this contact is opened and relay 408 is isolated before the full operation'of the dash pot relay 283. Thus, the ultimateengagement of the bridging member 204 of the dash pot relay Zvith its contacts isy ineifective to operate relay 98. l

Because of the .relatively unskilled operators employed at the lbranch oices, the start switch 6| may be operated to itsright hand contact and almost immediately restored to its left hand contact. In accordance with the foregoing description the operation of thi-s switch to its right hand contact causes the central ofce switching equipment to respond and, if an idle recorder is available. to make aY connection between it and the branch omce. This connection is normally made in a Very short time so that, when Ythe switch 6| Vis quickly moved to its left hand contact, concentrator relay 383 is released to; release relay 321, the purpose of which normally i5 to initiate Iscanning at the recording apparatus. However, relay 308 soon releases its armature 351 because the simplex signaling current is not sufficient to reoperate relay 11.- Engagement of Varmature 391 of relay 388 with its back contact operates relay 303 which in turn reoperates relay 321. YWhen the armature 328 of this relay is rst released fromv its front contact, the circuit through winding 336 of relay 331 is interrupted and the condenser 338 begins to discharge through the resistance 34|. This resistance is of a relatively high value so that the condenser requires four or five seconds in which to become completely discharged. Consequently, the reengagement of armature 328 with its front contact Y almost immediately thereafter does not produce a large charging current through the winding 338 of relay 321 since the condenser 338 is only slightly discharged. The value of this small charging current is insuflicient to operate relay 331. started under these conditions.

The reengagement of arm-ature 43| of relay 321 with its front contact closes a circuit through the back contact and tongue 432y of relay 433 and the winding 4|4 of relay 29,2. At the same time the winding 433 is also energized to disengage the armature 432 from its back contact. However, before the operation of armature 432 the circuitthrough winding 4|4 of relay 292v is completed for a sufficient time to allow this relay to disengage its tongue 29| from its back contact. The momentary opening of this contact interrupts the locking circuit for the concentrator relay 8|, thereby releasing the switching equipment to its idle condition. Thus, it is seen that the rapid manipulation of the branch officev switch 6| as described does not interfere with the normal operation of the central oflice switching and recording apparatus.

Facilities are provided in the concentrator switching equipment so that 'one or more branch offices may be provided with a preferred type of service. This is desirable for the reason that the apparatus is so arranged that, inthe case'of two simultaneously initiated branch office calls, the switching apparatus associated with the lowest numbered recorder starts seeking one of the calling branch oilice circuits. From the foregoing description it is apparent that the stepping switch 69 is arrested assocn as one of the calling branch ofiice lines is located. Normally, hcwever the desired connection between one of the branch Oifices and a central ofce'recorder is quickly established and the concentrator apparatus switched to another unit associated with Therefore, the drum changing cycle is not another idle recorder. In this manner the second calling branch oflice is provided with its desired connection to a recorder with only a slight delay. The delay in a case of thi-s nature is so small that the connection is completed before the branch ofce amplifier equipment has had an opportunity to become operatively conditioned.

However, in the case where all of the central oflice recorders are busy, an incoming call results only in the operation of relay 'll and relay 234. The operation of this latterA relay applies a ground through the armature 252 to the conductor 254 so that as soon as one of the recorders is released the remaining switching apparatus may be operated as described. If two or more branch ofhces initiate calls at a time when all central oice recorders are busy, their associated line relays, similar to relays 11 and 204, are operated to also apply grounds to conductor 254 by which these sub-stations make a bid for connection to a recorder. As soon as one of the central oflice recorders becomes available for a new connection the stepping switch 69 associated with this recorder is operated until it becomes connected with one of the branch office lines, not necessarily the line over which the first call was initiated. Consequently, the other branch offices must wait until another central office recorder is released and it will be seen that, under adverse conditions, the first calling substation may be made to wait for a considerable time.

Any one or more of the substations may be provided with apparatus which will insure the branch office of a connection with the central ofce recorder which first becomes available. Such a provision may be made by moving a switch 434 of Fig. 4 to its right hand contact. When the substation associatedvwith this unit of the switching equipment initiates a call to opcrate relays 'il and 204, the engagement of armature 252 of the latter relay with its front contact, in addition to applying the ground to conductor 254, energizes a relay 436. The operation of the armatures 431 of this relay to their respective front contacts applies' a ground to the contact studs of all other branch oice' lines except the one associated with the preferred branch ofce. Therefore, if, when the preferred branch ofce puts in a call to the central office, all of the recorders are busy and a number of other branch office calls may be waiting ahead of it, the stepping switch which is associated with th'e rst released recorder will pass over the contact studs associated with the branch ofce linesawaiting connection and will not stop until the lines associated with the preferred branch oice are located.

Inserted in the conductors over which the facsimile signals are transmitted to the central oiice recording apparatus are a number of switch contacts. Since the potential of the facsimile signals is relatively low there is the possibility that suflicient contact resistance may exist in the circuits to mutilate the signals. Provisions are made herein to obviate such a condition. When the desired connection between the branch ofce transmitter and the central office recorder is established, the positive potential of conductor 3l6 (Fig. 4) is applied to the midpoint of the inductance 'Z4 as described. Between the line conductors L and the amplifier 62 are two of the contacts of the stepping switch S9 and the tongue 294 and front contact of relay 8i in series with the conductors comprising the facsimile circuit. A relatively high resistance 438 is bridged across the conductors 439 and 44 which extend the facsimile circuit respectively from the front contact associated with tongue 294 of relay 8l and the wiper 18 of the stepping switch 69 to the amplifier 82. All of the contacts included in the facsimile circuit therefore Vlie between the in'- ductance 14 and the resistance 438. The midpoint of resistance 438 is connected to thel negative potential of conductoru2'4l. AThus, it is seen that kthe combined potential of the batteries 248 and 3 Il is impressed across the contacts vincluded in the facsimile circuit. This potential is considerably greater than that of thekfac'simile signals and is adequate to prevent.v theformation of a film on any of the contacts and thereby insures a low resistance of such contacts. The direct current which is applied to the conductors 438' and 44| is prevented from reaching the ainplier 82 by the inclusion of blocking condensers 442 and 443 in series with the respective conductors at points between the resistance 439' and the amplifier. y

lThe automatic switching apparatus shownin Fig. 4 may be expanded to accommodate a large number of sub-stations having the transmitterreceiver apparatus of Fig. 3 and a suitable number of central station recorders such as shown in Fig. 5. The number of the latter will be determined by the probable simultaneous service demands of the sub-stations. A group of line relays such as ll, 204 and 208 of Fig. 4 is necessary for each sub-station connected to the switching equipment. For each central ofce recorder employed in the system relay equipment vcorrespondingv to that, except the aforementionedrrelays, shown outside of the dotted lines of Fig. 4 is required.

The nature oi the invention may be ascertained from the foregoing description of an illustrative embodiment, it being understood that changes in the invention herein disclosed may be made within the scope of what is claimed without departing from the spirit of the invention'.

What is claimed is:

1. In a facsimile telegraph system, a plurality of facsimile transmitters, a plurality of facsimile recorders located at a central station, switching means individual to eachrof said recorders and associable with any of said transmitters, means at said central station lresponsive to a signal initiated at one of said transmitters for operating one of said switching means to connect said signal initiating transmitter with oneV of said recorders, and means controlled by said switching means and responsive to the establishment of said connection to initiate scanning by said one transmitter.

2. In a facsimile telegraph system, a plurality of branch stations having facsimile transmitting apparatus, a main station having a lesser plurality of facsimile recorders and a multi-contact stepping switch individual to each of said recorders, means including said switches, for associating any of said recorders with any of said transmitters, means at said branch station for transmitting a calling signal, means responsive to a calling signal when one of said recorders is idle to operate one of said switches, means including said calling signal responsive means for holding a call at said main station when all recorders are busy, and means for `connecting said calling signal transmitting station to the first recorder which becomes idle.

3. In a facsimile telegraph system, a plurality of facsimile transmitters, a plurality of facsimile recorders located at a central station, a multicontact stepping switch associated with eachof said recorders and adapted to establish connection to any of said transmitters, means at said central' station responsive to a calling signal from one of said transmitters to render operative the switch associated with an idle one of said recorders for locating the calling transmitter, andmeans including said operative switch to connect said calling transmitter with said idle recorder.

4. In a facsimile telegraph system, a plurality of facsimile transmitters, a plurality of facsimile recorders arranged in a predetermined sequence, a Vmulti-contact stepping switch associated with each of said recorders and adapted to establish Vconnection to any of said transmitters, means responsive to a calling signal from one of said transmitters to render operative the switch associated with the lowest numbered idle one of said recorders for locating the calling transmitter, and Vmeans including said operative switch to connect said calling transmitter recorder. Y y i 5. In a facsimile telegraph system, a plurality of facsimile transmitters, a pluralityY of facsimile recorders, means including a connector relay for each of said recorders operable to connect its associated recorder to any of said transmitters, an answer-next relay for each of said recorders, the contacts ofsaid answer-next relays being interconnected and positioned according to the busy or idle condition of their associated recorders, and means including said answernext relays toy render those of said connector relays associated with busy recorders unresponsive to a signal initiated at one of said transmitters and to render the one of said connector relaysfassociated with an idle recorder responsive to said signals.

v 6. In a facsimile telegraph system, a plurality of facsimile transmitters, a plurality of facsimile recorders, means for connecting any of said transmitters with any of said recorders, an answer-next relay for each of said recorders, the contacts of said answer-next relays being interconnected and positioned according'to the receptive or non-receptive condition of their asso-2 ciatedrecorders, and means for preventing the connection ofa transmitter to4 an idle recorder when the latter is notconditioned forvreceptionf 7. In a facsimile telegraph system, a plurality of facsimile transmitters, a plurality of facsimile recorders, a switch responsive to a signal initiated atV one of said transmitters toy connect said one transmitter to one of said recorders, a relayv to control the scanning function of said one recorder, means responsive to the establishment i. of said connection to prepare said relay for exercisingfits control function, and means responsive to theoperative conditioning of said one transmittern for actuating said relay to initiate the scanning function of said one recorder.

8; In al facsimile telegraph system, facsimile apparatus including a transmitter and a recorderj a signaling circuit interconnecting said transmitter and said recorder for correlating the scanning functions of said facsimile apparatus, means at said recorder effective after the operative con- Vvditioning thereof for periodically transmitting phasing signals over said circuit, a rst relay at said transmitter responsive to the first of said phasing signals to initiate scanning by said transmitter, and Va second relay at said transmitter with said Iidle f for rendering said first relay unresponsive to phasing signals received subsequent to'said flrst signal, said second relay being responsive to a disconnect signal transmitted over said circuit ductors, impedances bridged across said conductors on either side of said contacts,k and a relatively high direct current potential connected between points of said impedances intermediate the terminals thereof to effect the circulation of direct current through the local circuits formed by said contacts and said impedances and thereby reduce to a minimum the resistance of said contacts to said alternating current signals.

10. In a facsimile telegraph system employing alternating current signals, a path for said signals including a conductor, a contact in said conductor, and a shunt circuit around said contact including a source of direct current potential whereby direct current is conducted through said Contact to insure a vminimum of resistance by said contact to said alternating current signals;

11. In a facsimile telegraph system, a plurality of facsimile transmitters including one having a preferredstatus, a plurality of facsimile recorders, means including stepping switches associable in a predetermined sequence with all Vof said transmitters for connecting any of said transmitters for communication with any of said recorders, and means for controlling one of said stepping switches to connect said preferred transmitter to the rst one of said recorders to become idle irrespective ofthe number of non-preferred transmitters awaiting connection to one of said recorders becoming associated with said switch before said preferred transmitter is reached.

12. In a telegraph system, Va plurality of transmitters, means responsive to a call originating at any of said transmitters for testing said transmitters invariably in a predetermined sequence, means for normallyarresting said testing means when a calling transmitter is located, and means responsive to a call originating at a preferred one of said transmitters for continuing the operation of '.said testing means until Asaid preferred transmitter Ais located irrespective of the number of other calling transmitters tested prior to the location of said preferred transmitter.

13. In a facsimile telegraph system, a'facsimile transmitter, a facsimile recorder, switching apparatus responsive to a calling signal originating at said Atransmitter for interconnecting said transmitter and said recorder for communica.

tion, means responsive to a phasing signal originating at said transmitter to initiate the scanning functions of said transmitter and said recorder and means responsive to a failure of the,

recorder to start scanning within a predetermined time after the actuationvof said phasing signal responsive means to prevent said switch-r ing apparatus from responding to another calling signal. Y Y

14. In a facsimile telegraph system, a facsimile transmitter, a facsimile recorder, switching ap-v paratus responsive to a calling signal originating' at said transmitter for. interconnecting said transmitter and said recorder for communica-V a phasing signal origi-v tion, means responsive to n nating at said transmitter to initiate the scanning functions of said transmitter and said recorder, and means responsive to a failure of the recorder to start scanning within a predetermined time after the actuation of said phasing signal responsive means to operate an alarm signal.

15. In a facsimile telegraph system, a facsimile transmitter, a facsimile record-er utilizing individual subject matter copyholders and provided with apparatus for automatically changing said copyholders, a signaling channel for interconnecting said transmitter and said recorder for communication, means responsive to a phasing signal originating at the transmitter to initiate the scanning functions of said transmitter and said recorder, and means responsive to a failure of the recorder to start scanning within a predetermined time after the actuation of said phasing signal responsive means te actuate said automatic copyholder changing apparatus.

16. In a facsimile telegraph system, a facsimile transmitter and a facsimile recorder, each having scanning apparatus, a signalling channel for interconnecting said transmitter and said recorder for communication, means responsive toa phasing signal to initiate simultaneously the movement of the scanning apparatus of said transmitter and said recorder, and means responsive to the non-receipt of facsimile signals during a scanning operation to arrest movement of the scanning apparatus of said recorder.

17. In a facsimile telegraph system, a facsimile transmitter, a facsimile recorder utilizing individual subject matter copyholders and provided with apparatus for automatically changing said copyholders, a signaling channel for interconnecting said transmitter and said recorder for communication, means responsive to a phasing signal originating at said transmitter to initiate the scanning functions of said transmitter and said recorder, and means responsive to the nonreceipt of facsimile signals during a scanning operation to actuate said automatic copyholder changing apparatus.

18. In a facsimile telegraph system, a facsimile transmitter, a facsimile recorder, switching apparatus associated with said transmitter and said recorder, means responsive to a calling signal originating at said transmitter for operating said switching apparatus to connect said transmitter and said recorder for communication, means responsive to a disconnect signal sent from said transmitter after a predetermined period following the transmission of said calling signal to disconnect said transmitter from said recorder and to recondition said recorder for reception,

y station individual to each of and means responsive to a disconnect signal sent during said predetermined period to disconnect said transmitter from said recorder and to prevent the reconditioning of said recorder for reception.

19. In a facsimile telegraph system comprising a plurality of facsimile transmitters, a plurality of facsimile recorders located at a central station, a multi-contact stepping switch individual to each of said recorders and associable with any of said transmitters, means at said central said transmitters and responsive to a calling signal originating at its associated transmitter to start one of said switches stepping over its contacts, means for stopping said switch on the contact associated with the transmitter originating said calling signal, and means including said stopped switch for connecting said calling transmitter with the recorder associated with said switch.

20. A facsimile telegraph system comprising a plurality of facsimile transmitters, a plurality of signaling channels each having one terminal thereof connected to respective ones of said transmitters and the other terminals thereof located in a central station, a plurality of facsimile recorders at said central station, a multicontact switch individual to each of said individual recorders and having the `contacts thereof connected to respective ones of the central station terminals of said signaling channels, a line relay connected to each of said signaling channels to actuate one of said switches in response to a calling signal originating at its associated transmitter, and means including said actuated switch for connecting the recorder associated therewith to the signaling channel associated with said calling transmitter.

21. In a facsimile telegraph system, a plurality of facsimile transmitters, a plurality of facsimile recorders located at a central station, means at said central station including a stepping switch associated with each of said recorders for operating in response to a calling signal originating at one of said transmitters to locate said calling transmitter, means operative upon the location of the calling transmitter to connect said calling transmitter with one of said recorders, and means controlled by said connecting means to initiate scanning at said calling transmitter.

WILLIAM B. BLANTON. FRANK LESLIE CURRIE. GEORGE W. JANSON. LOUIS G. STEWART. RALEIGH J. WISE. 

